In mass production of DVRs, how to economically and rapidly provide different video signals to each DVR for burn-in becomes an important topic at the test stage. The burn-in for the DVR means the video signals with different compression ratios are fed, e.g., in a high-temperature environment, into the DVR to increase the load of the DVR during the test stage. The burn-in confirms the DVR can operate stably in such high-temperature environments. The high-temperature environment is created, in general, in an oven with the temperature ranging from 40° C. to 50° C. In addition, the conditions of the burn-in change depending on customers' requests; for example, whether the DVR can endure a continuous seven-day-long burn-in at 50° C., or increasing the environmental temperature gradually (generally performed in a temperature-controlled oven) until the DVR shuts down. Also, the number of video signal input channels may vary, and four, eight, or sixteen video signal input channels are commonly used.
FIG. 1 shows a conventional video signal system configured with sixteen video signal input channels, which comprises five amplifiers (one is a first amplifier 11 and the other four are second amplifiers 13), and twenty-one signal cables C1-C21. Each amplifier (11 or 13) has one input port and four output ports. First, a video signal VA1 (obtained by a video capture equipment such as a video recorder, or a monitor) is transmitted through a signal cable C1 to the first amplifier 11. Then, the video signal VA1 is divided into four video signals VA1-1-VA1-4. The four video signals VA1-1-VA1-4 are transmitted through four signal cables C2-C5 to the four second amplifiers 13 as input signals, respectively. Next, sixteen video signals VA2-1-VA2-16 from the four second amplifiers 13 are transmitted through sixteen signal cables C6-C21 to a device under test (e.g., DVR). If the DVR under test has sixteen video signal input channels, the video signals provided by the video signal system of FIG. 1 can only meet one DVR's requirement. If ten DVRs need to be tested at the same time, the layout of the signal cables will be complicated and chaotic (at least 210 signal cables and 40 amplifiers required).
Therefore, the conventional video signal system of FIG. 1, used at the test stage in mass production, will result in the problems as follows. First, when numerous DVRs under test need to be tested simultaneously, incorrect wiring of the numerous signal cables occurs easily. Second, much human effort is needed to correctly connect the signal cables to the corresponding DVR under test. Third, the layout of the signal cables in FIG. 1 is prone to cause an impedance matching issue and thus, distorted video signals. Fourth, when numerous DVRs under test need to be tested simultaneously, they are placed in a large temperature-controlled room. In general, the manufacturers of DVRs rent the large temperature-controlled room from an external research institute; for example, a certified laboratory in the Industrial Technology Research Institute of Taiwan. In the rented room, complicated and messy signal cables are absolutely not allowed. Fifth, the video signals in the signal cables are affected by high temperature (about from 40° C. to 50° C.) during burn-in, and accordingly, the test result is affected. Sixth, to meet different customers' requirements, different video patterns have to be available. Even for a single customer, video patterns with various complex degrees are required to perform the burn-in process; for example, video patterns with various compression ratios. If the conventional video signal system of FIG. 1 is used, the source (e.g., a monitor) of the video signal VA1 has to change and thus, it is very inconvenient to perform the burn-in process in such a large temperature-controlled room.
To solve the above problems, it is necessary to develop a video signal generator providing adjustable video patterns to rapidly and economically perform video signal testing of DVRs.